FullCalendar Angular 13 error when importing npm library - npm

Question

I have an npm library which imports Angular FullCalendar v5 and everything works fine there. When i try to import my project library to another project and try access the full calendar frontend I got a warning and a message error in my browser console:
- Warning: main.js:7358 Unknown option 'default'
- Error: core.mjs:6476 ERROR TypeError: Language ID should be string or object.
at new DateTimeFormat (<anonymous>)
at buildNativeFormattingFunc (main.js:1218)
at NativeFormatter.buildFormattingFunc (main.js:1211)
at NativeFormatter.buildFormattingFunc (main.js:1009)
at NativeFormatter.format (main.js:1154)
at NativeFormatter.formatRange (main.js:1169)
at DateEnv.formatRange (main.js:3984)
at CalendarDataManager.buildTitle (main.js:6909)
at CalendarDataManager.buildTitle (main.js:1009)
at CalendarDataManager.updateData (main.js:7113)
I can't figure it out why but i know it's in this line of code at main.js (#fullcalendar/common/main.js)
Line 1218 -> var normalFormat = new Intl.DateTimeFormat(context.locale.codes, standardDateProps); The error is that the variable context.locale.codes is undefined.
Can anyone help?

Answer 1

I've just had the same error. Not that I was importing a project library of my own but I was importing the Fullcalendar library (from node_modules). I had enabled localization using the locale property of the calendar options but I always got this error Language ID should be string or object.
Two things was wrong:
I was importing the locale code incorrectly which resulted in this error. The current version of Fullcalendar (6.0.0) has all its locale code under #fullcalendar/core/locales.
I was using dynamic import like this: import("#fullcalendar/core/locales/da") and it worked fine but I had to access the default property of the exported object. Using async/await syntax it becomes:
const localeModule = await import("#fullcalendar/core/locales/da");
const calendar = new Calendar(someElement, {
(...),
locale: localeModule.default
});
Not directly answering your question but it sounds like you're using locale, too, and your other project is importing your project library in a way that makes the default property of the module containing the locale code undefined.